Method of making soft papers adaptable to impregnation



Jan. 19, 1954 N. J. NIKS 2,656,369

METHOD OF MAKING SOFT PAPERS ADAPTABLE TO IMPREGNATION Filed May 29, 1952 v INVENTOR NICHOLAS d- IV/KS :v

M kw ATTORNEYS Patented Jan. 19, 1954 UNITED sures PATENT cr mes METHOD or an-mo SOFTIAPERS ABLE TO manouarrou lNicholasJnNikaMunisi-ngMiz-h. Application Mans, 1952 SerialN0..290,548

' 2 Claims. 1

This invention relates to a method andapparatus for -=manu-faoturing paper, and particularly this invention relates to a method and a paratus for manufacturing paper especially adapted for impregnation.

This application is a continuation-in-part of application Serial No. 7 145337, filed September it, 1947, now abandoned.

In many instances it is desired that a paper stock be of a nature whieh-w-ill-make it adaptable for impregnation by various substances. Papers 'of this nature are employed as electrical insulation, as fabric substitutes, as cleaning members and for many other purposes. It is essential to the quality of the impregnated articles to be made that the paper from which it is made be capable of receiving andre'taining a substantial quantity of the impregnating material. At the same time *i-tis often desired for the paper to have relatively high strength. This is particularly true when the impregnated paper is to be used as electrical insulation or as a fabric substitute. I V p 'In the usual manufacturing "process for paper, the paper stock flows on to a wire-conveyor belt and the water is drained therefrom either by gravity or by the application of a vacuum. Thereafter the paper is sub'jeeted to calendaring and drying operations performed by heated rolls or heated plates. The substantially dried paper is then rolled up and passes through a finalrdrying operation immediately before it is received on the take up rolls. This manner of treating the paper stock naturally compresses the fibers together and a moreor less dense and hard paper results. Such papers are not easily impregnated andwhen they are impregnated naturally do not retain a great deal of the impregnant. Furthermore, there maybe hard spots in the paper which impair its utility as a cleaning member 'or :as electrical insulation, these hard spots being abrasive, or having low dielectric strength due to their lack of impregnating material.

According to the present invention a method of manufacturing paper is provided wherein a thoroughly dried product is supplied to a take up roll but which has been dried without the application of pressure thereto. This results in a paper in which the fibers are not pressed together but lie in an open'pattern ideally suited for receiving and retaining impregnating materials, Furthermore, the individual fibers are loose and unpressed'so that not only is the paper as a whole very receptive to impregnants but each fiber there is inia l'condition to receive (01. era-389' and retain a maximum amount of the "impregnating material.

It is accordingly, a primary 'object pt this invention to provide a method for manufacturing paper which will be h'ighly porous and therefore adapted for receiving impregnated materials.

Another object is the provision of a method of manufacturing paper without the use of drying and ealenderingrd-l-ls. v I

A further object is the provision of a paper making machine adapted for operating in accordance with the methods described above.

further object is to provide a method of manufacturing paper having improved absorlbent properties, and wherein the process "is carried outin a continuous and rapid manner without the use of conventional squeezing rollers.

Another object 'of the invention is the prove sion of a method and apparatus for producing paper in which the fibers forming the paper are not compacted together but remain loosely united forming a soft, 'iiufly mess. I

stillanother object is to provide a method of making highly absorbent paper of the "character described utilizing vacuum treatment only dur; ing the initial stage or stages, and whereby the major amount ofthe water is removed without causing any appreciable compacting together of the fibers. Thereafter the paperstock is subjected to a penetrating infra-red heat treatment, as the same is moved along on an endless conveyor, to remove substantially all of the moisture remaining in the paper prior to rolling the. same up on storage rolls.

These and other objects and advantages will become more apparent upon reference to the following description taken in connection with the accompanying drawings wherein there is illustrated a paper making machine according to this invention.

Referring to the drawings, there is illustrated a paper making machine generally of the Fourdrinier type wherein the paper stock passes from a stock box it) beneath a slice 12 onto a I wire belt M. The slice may be adaptable by means of the hand wheels it in any of several manners well known in the art in order to regulate the thickness of the layer of paper stock at 18 which fio'wsento the wire belt 14.

The wire belt 14 passes over a pair of rolls 20 and one thereof is adapted for being driven by a motor 22. The belt 4 is of such a mesh that it will support the fibers of the paper stock but allow relatively free drainage therefrom of the water. The water which flows from the stock through the belt [4 is collected in a catch basin 24 which is connected by a pipe 26 with a source of vacuum. The application of vacuum greatly increases the rate of flow of the water from the stock and permits the process to be carried out as a continuous process. The paper stock at this point contains a high percentage of free water and thus the application of forced draining thereof does not operate to cause matting together of the fibers.

To effect the removal of the major portion of the water quickly, yet not cause packing or matting together of the fibers, preferably a vacuum of about 1 to 15 inches Hg is applied in the suction line 26.

In the manufacture of very light weight papers preferably no vacuum is used. In the case of six to eighteen pound papers, the vacuum used is from about 1 to 4 inches of Hg. This vacuum is increased upwards in direct proportion to the increased weight of the paper that is being produced. For instance, for very heavy paper the vacuum is increased to about 15 inches HgJ In this way, by controlling thevacuum so that it is directly proportional to the weight of the paper being produced, and yet is high enough to quickly remove the greater part of the water from the stock, the process may be carried out in a continued manner and under conditions to produce a paper which is very porous and fluffy regardless of its weight or thickness.

The invention thus provides an improved and inexpensive method of making soft fluffy paper by causing the paper to form on a moving wire support in the absence of pressure sufficient to bring about compacting of the fibers, and which thereafter is subjected to a penetrating drying heat which effects the removal of water and drying of the papers fromthe central portion outwardly so that there results a paper sheet wherein the fibers are loosely held together and which present an open fiber structure.

While paper making processes heretofore have utilized suction boxes and different degrees of suction, insofar as known, it has not been the practice to produce a paper of the-character described by fiowing the paper stock onto a wire belt conveyor and initially applying a vacuum directly proportionate to the weight of the paper to be produced, and then transferring the initially de-watered stock to a felt conveyor whereupon the remainder of the water is removed by gravity and under the action of infra red heat waves.

A relatively high vacuum may be used in the initial stage when a comparatively large amount of water is present which surrounds the fibers and prevents them from matting or packingtogether. During this initial stage the large excess of free water passes through the wire mesh openings in the conveyor belt l4. After the removal of this excess water from in between the paper stock fibers, vacuum-draining of the pulpy mass must be discontinued otherwise packing and matting of the fibers occurs which results in the production of a paper which is not as fluffy and absorbent as otherwise would be produced. It is thus a critical feature of the process to apply suction only during the initial stage of the process when excess water is present.

After a predetermined travel on the wire conveyor belt I4; during which the mass is subjected to suction to draw off substantially all of the free water, the pulpy,

moist layer of 4 fibers is passed to a second conveyor belt as at 23 which is preferably a felt. As the fibrous mass passes from the belt M the vacuum is released. It is an essential feature of the process to apply suction only during the initial stage when water can be removed rapidly from the pulpy mass without causing any packing or matting of the fibers which would prevent the formation of a fiuffy highly absorbent paper.

The paper stock mass delivered to the felt belt 28 still contains considerable water. This water is removed at a relatively slow rate by gravity, the water passing through the belt conveyor belt 28 and into the drip pan 30 beneath the belt. Similarly as the belt 14, the belt 28 passes over a pair of rolls 32 one of which is driven, as by the motor 34.

After the paper stock has remained on the belt 28 for a predetermined length of time, and during which time practically all of the remaining water is removed therefrom, it passes to a third conveyor belt 36, which is also made of felt. The belt 36 passes over a pair of rolls at one of which is suitably driven, as by the roll 32 which is drivingly connected to the motor 34.

During the travel of the paper stock over the last part of the conveyor belt 28 and the first part of the belt 36, or after it has left the belt 28 it is subjected to a drying treatment by the heating device indicated at 40 which is spaced above the paper layer and which transmits heat to the said paper by any suitable radiant heating means such as infra-red lamps, strip heaters suitably backed up by reflectors, or similar apparatus.

The action of the radiant heating device at 46 is such that substantially all of the remaining moisture in the paper layer is evaporated therefrom. It will be noted that there has been no application of pressure to the paper stock during its travel over the felt conveyors. The suction applied during the initial stage permits the rapid removal of excess water and thus speeds up the process, and the fibers in the finished paper are thus left in an open condition and ideally suited for receiving impregnating material.

The application of radiant heat, which penetrates into the center of the paper layer, is also beneficial in the formation of paper according to this invention because the vaporizing of the moisture in the stock operates to produce a fiuifing action which prevents the formation of pockets and hard spotsin the paper. The fluffy characteristic property is further enhanced due to the absence of any pressure during the removal ofthe moisture and drying of the paper stock. I

The paper layer passes from'the conveyor belt 36 over a pair of heated drying rolls 42 and thence to. a take up station 44 which is driven by a motor 46. Since the paper layer is substantially completely dried before it passes over the rolls 42, there is no matting together of the fibers in the paper layer. The rolls 42 are thus merely for the purpose of insuring that all of the moisture is driven from the paper before it is rolled up.

After the paper has been manufactured it may thereafter be impregnated by any suitable means which may include dipping, by pressure, by forcing the impregnated material into the paper by rolls, or any other suitable manner;

It is to be noted that the treatment of the' paper stock is carried out entirely in the absence of pressure until the stock has dried to the point where a final application of heat and pressure will not operate to mat down and compress the fibers of the paper. The water is removed from the stock at a rate generally in proportion to the water content whereby the fibers remain loose and open for receiving impregnants.

It will be evident that paper manufactured by the method of this invention is especially receptive to impregnating materials but at the same time may have a high strength because substantially any paper stock can be converted into a paper adapted for impregnation by this method.

It will be understood that this invention is susceptible to modification in order to adopt it to different usages and conditions and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

I claim:

1. The manufacture of soft paper of light weight as a continuous process which consists of the steps of establishing an aqueous paper stock, flowing said paper stock onto an open-mesh conveyor, rapidly removing a major portion of the water in the stock by the application of a relatively high vacuum of about 1 to 15 inches mercury, thereafter discontinuing said vacuum treatment upon removal of the excess water to prevent packing and matting of the paper stock fibers, transferring the thus treated web of paper fibers to a second conveyor of felt and removing the remainder of the Water from the paper web by gravitation onto the felt surface while the paper Web is conveyed along, and subjecting the resultant paper web to infra-red heat to produce a finished paper which is of extremely light weight and wherein the fibers of the paper remain open and fiufiy.

2. In a process of continuously manufacturing paper comprising treating an aqueous paper stock to remove water on an open-mesh screen and form a substantially dry paper sheet which consists of the improvement steps of subjecting said paper web to a relatively high vacuum treatment of between 1 and 15 inches of mercury during the initial stage of water removal only and while the paper stock is conveyed along in the form of a web, and terminating said vacuum treatment after removal of substantially all of the excess free water of the paper stock web and before packing and matting of the fibers takes place, removing the remainder of the water from said paper stock web by gravitation, and applying heat to dry the resultant paper web and produce a finished paper product which is soft, fiufiy and wherein the fibers remain loose and open.

NICHOLAS J. NIKS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,163,252 Millspaugh Dec. 7, 1915 1,315,924. Fuller Sept. 9, 1919 1,843,656 Tompkins Feb. 2, 1932 1,891,027 Richter Dec. 13, 1932 1,909,083 Williams May 16, 1933 1,951,714 Tompkins Mar. 20, 1934 1,968,437 Boughton July 31, 1934 2,429,338 Adams Oct. 21, 1947 

